3rd generation partnership project (3GPP) long term evolution (LTE) is an improved version of a universal mobile telecommunication system (UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.
In general, discontinuous reception (DRX) is a scheme in which UE monitors a downlink channel discontinuously so that the consumption of a battery is reduced. When DRX is configured, UE monitors a downlink channel discontinuously. If DRX is not configured, the UE monitors a downlink channel continuously.
Recently, lots of applications require an always-on characteristic. The term ‘always-on’ means a characteristic in which UE is always connected to a network and it can send data immediately if necessary.
If UE continues to access a network, however, the consumption of the battery is great. For this reason, if DRX suitable for a corresponding application is configured, the consumption of the battery can be reduced and the always-on characteristic can be guaranteed.
As small cells having small coverage, such as a pico cell and a femto cell, are recently introduced, the mobility of UE has increased. In this wireless communication system, there is a new discussion on an optimal DRX configuration, change and/or application thereof in relation to interference from neighbor cells, a measurement report, and handover.